I thought I had beaten the rust finally. No such luck.
The area around the point where the radius arm fixes to the body via the cup unit was badly decayed on both sides. Luckily once the old cups were removed the repair was quite simple.
(one side had been repaired before and disguised with bathroom sealer!!!!)
However, is there a way of ensuring the cups are located in the correct position prior to final fixing? I am concerned the axle will not ride correctly.
As always, many thanks.